1. Field of Invention
The present invention relates to a screw feeding apparatus and more particularly, to a fluid-driven screw feeding apparatus for automatically and separately feeding a plurality of continuously fed screws into power drivers (not shown).
2. Prior Art
Conventionally, previously proposed apparatus of the above described type, for example, in Japanese Pat. No. 44/24831, in which it is so arranged that, while 2 pieces of small screws are supplied into separate power drivers, the piston is brought into sliding movement for moving the screw feeding plate and intercepting plate coupled to said piston so as to cause the small screw at the lowest position on the rails to stand by on the support plate following the movement of the piston, and upon completion of the reciprocation of the piston, said small screw is spontaneously dropped into a vertical hole in the main unit for standing by, with a second small screw being subsequently made to stand by on another support plate, so that, as the piston returns to the original position, said small screw is caused to spontaneously drop into another vertical hole and to stand by in the screw feeding hoses communicated with respective power drivers through the vertical hole formed in the intercepting plate. Upon opening of the electromagnetic valve, compressed air is directed into the hose so as to separately supply the screw standing by in said hose into the power drivers, and simultaneously acts one end face of the piston to drive said piston. However, the screw fed from the rails is held, at its neck portion in two directions, in the U-shaped slit of the screw support plate moving back and forth and confronting the direction of advance of said screw, and during retreatment of said support plate, only the screw strikes against the end face of the screw feeding plate reciprocating at right angles with respect to the advancing direction of the screw so as to be prevented from moving in the horizontal direction for being dropped into the vertical hole of the auxiliary feeding plate. The known arrangement as described in the foregoing, however, has such disadvantages that, since said screw is held from two directions when supported by the screw support plate, the screw itself is not positively driven in the horizontal direction and tends to get out of place before advancing up to the position of said vertical opening, thus distribution of screws not being positively effected. Meanwhile, although the screw is held at its neck portion from two directions by the U-shaped screw support portion provided at the forward end of the support plate, it is so arranged that the screw is prevented from retreating at the forward end of the screw feeding plate so as to be disengaged during retreatment of said support portion, and is spontaneously dropped into the vertical hole at the lower portion, while the upper portion of the vertical hole is not formed into the cylindrical shape, but in the so-called waning circle, which brings about such a problem that smooth dropping of the screws cannot be expected, for example, by the lower edge of the screw head caught by the entrance of the vertical hole. Moreover, the known arrangement as described above gives rise to such an inconvenience that there sometimes arises a case where, after dropping of the two screws into the feeding hose, the screw feeding compressed air is fed into the screw feeding hose immediately before the complete shutting off of said vertical hole by the screw opening intercepting plate, and thus, the compressed air is also direvted upward in the vertical hole so as to blow up the subsequent screws on the support plate upwardly.